So far, with getting better gear my dmg is increasing aswell, around 2k-2,5k dmg at the moment.
I've looked up the hit rating cap for deathknights, which according to some sites is about 295, but then there is the discussion of the hit rating with spells that differs for the Deathknight that is unholy, it should be more if that's the case.
Since I'm mostly Blood specced and already over 300 hitrating I am now focussing on strength and AP, got some enchants and gems that should help me out, yesterday.
So i'll see if and how that improved me